Expanding valves for electrostatic precipitators and the like

ABSTRACT

A flow control system for an electrostatic precipitator or the like comprising a plurality of elongated inflatable fabric bags used as valves to stop gas flow to the precipitator or through selective portions of the precipitator when such bags are inflated.

United States Patent Spehrley Aug. 19, 1975 [54] EXPANDING VALVES FOR 3,011,518 12/1961 Day et a1. 137/601 ELECTROSTATIC PRECIPITATORS AND 313294163 7/1967 Barker THE LIKE 3,593,645 7/1971 Day 98/40 VM 75 Inventor: Charles w. Spehrley, White River FOREIGN PATENTS OR APPLICATIONS J ti Vt, 1,232,964 5/1971 United Kingdom 251 5 339,625 7/1921 Germany 55/112 [73] Asslgneet Joy Man fac ring Comp ny, 539,921 2/1956 Italy 55 110 Pittsburgh, Pa. 251,848 2/1968 U.S.S.R 251/5 [22] Filed: June 6, 1973 OTHER PUBLICATIONS [2]] App} 367,460 German Printed Application No. 1,090,642, printed Oct. 13, 1960, 4 pages.

12?} 111 .3'.5;;JJJJJJJIJJIJJJJJJJJ.557i?3511 156512131 Primary We [58] Field of Search 55/133, 110, 111, 112,

1 55/128, 129, 417, 108, 432, 4, 12, 13; [57] ABSTRACT 137/599, 601; 98/40 R, 40 V, 40 VM A flow control system for an electrostatic precipitator or the like comprising a plurality of elongated inflat- {56] References Cited able fabric bags used as valves to stop gas flow to the UNITED STATES PATENTS precipitator or through selective portions of the precipitator when such bags are inflated. 1,931,356 10/1933 Porter 137/601 UX 2,889,892 6/1959 Schaub et a1. 55/432 9 Claims, 16 Drawing Figures PATENTED AUG 1 91975 SliZU 1 n; 3

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EXPANDING VALVES FOR ELECTROSTATIC PRECIPITATORS AND THE LIKE The need for a flow control system for electrostatic precipitators or other gas handling apparatus such as that described and illustrated in the present application arises largely because of the necessity of including a plate cleaning interval in the operation of such precipitators wherein dust is shaken loose from collecting plates as by rapping and allowed to fall to the bottom of the precipitator for collection and disposal. During such a cleaning interval it is advantageous to stop or reverse the flow of gas through the section of the precipitator being cleaned. If such flow interruption is not employed there is almost always produced a puff of dust which flows out of the smoke stack and may be observed as an indication of lack of environmental con cern by the company operating the plant under consideration. There is also of course a reduction in the time- I average efficiency of the precipitation operation when such puffs are produced.

Many ways have been tried for stopping or reversing flow through portions of a precipitator but with little success due to the factors of heat, dust, corrosion and inaccessibility making it difficult to maintain satisfactory operation of mechanical devices in such a hostile environment. With the apparatus of the present invention no mechanically active devices within the flow path are necessary to provide the desired flow control.

The system of this invention which can essentially stop the flow during the cleaning interval will provide some or all of the following advantages;

Unsightly puffing will be eliminated.

A slight increase in overall timeaverage efficiency will be realized due to this lack of puffing.

Flow stoppage will allow rapping with the electric field turned off with the result that electrostatic adhesive forces are removed so that the plates may be rapped cleaner.

Thinner dust coatings on the plates due to cleaner rapping will promote higher efficiency of the precipitator especially in high resistivity dust conditions.

Since no puffing will be associated with the rapping cycle more frequent rapping and consequently higher efficiency is likely to be practical. I

These and other advantages and objectives of this invention will become more readily apparent upon consideration of the following description and drawings in which:

FIG. 1 is a fragmentary perspective view of the downstream end of a precipitator constructed according to the principles of this invention;

FIG. 2 is a schematic representation of a portion of an electrostatic precipitator incorporating the bag valves of this invention;

FIG. 3 is a schematic representation of a portion of a precipitator employing the bag valves of the present invention in a somewhat different arrangement than that shown in FIG. 2;

FIG. 4 is a further schematic representation of the apparatus of FIG. 3 with different conditions existing;

FIG. 5 is a schematic representation of a cross section of an inflated filter bag;

FIG. 6 is a schematic representation of a cross section of the filter bag of FIG. 5 in a collapsed state;

FIG. 7 is a schematic representation of the cross sectional shape of the end portions of two bag valves constructed according to the principles of this invention;

FIG. 8 is a schematic representation of a central portion of the filter bags of FIG. 7 when completely deflated;

FIG. 9 is a fragmentary sectional view of a portion of an electrostatic precipitator provided with bag valves according to the present invention;

FIG. 10 is a sectional representation of the precipitator shown in FIG. 9 taken substantially on line 10l0;

FIG. II is a cross sectional view of a bag valve constructed according to the principles of this invention;

FIG. 12 is a fragmentary side elevationalview of the bag valve of FIG. 11;

FIG. 13 shows a fragmentary portion of a precipitator employing bag valves of the type shown in FIGS. 11 and 12;

FIG. 14 is a plan view of a thimble to be used with the filter bags of FIGS. 12 and 13';

FIG. 15 is a sectional view taken substantially on line 15-15 of FIG. 14;

FIG. 16 is a fragmentary view of a filter bag with a second embodiment of an upstream support.

Referring now to the drawings, FIG. 1 shows, in perspective, the downstream end of a portion of an electrostatic precipitator constructed according to the principles of this invention and generally indicated at 20. The precipitator 20 is of a well known type provided with vertically extending collecting electrode curtains 22 which would normally be connected to ground and having between the curtains 22. vertically extending discharge electrode wires 23 (see FIG. 2) maintained dur' ing normal operation at a potential of perhaps 35,000 volts to provide the electrostatic action of the precipitator in a well known manner. The curtains 22 are parallel to each other, laterally spaced part, for example 9 inches as standard, and extend parallel to each other forming passageways 24 therebetween for the flow of gas to be cleaned therethrough. The curtains 22 normally are terminated somewhat below ceiling or roof of the precipitator but in the case of a precipitator constructed according to the principles of this invention either the curtains themselves at each side of a valved section or extensions impervious to gas flow such as indicated at 25 must extend the passageways 24 to the top of the precipitator and as at 25A down into the hopper in order to prevent cross flow of gas during valve action as will hereinafter appear.

In FIGS. 1 through 4, 7, 8, 10, 11, 12, 14 and 16 broad arrows 26 are used to indicate direction of gas flow through precipitators and relative to filter bags constructed according to the principles of this invention. For instance in FIG. 2 the gas flow will be from the bottom up as indicated by arrow 26 except that in FIG. 2 the passageways 24 controlled by bags 8, 9 and 10 have been completely blocked and no air flow will take place therethrough with the bags 8, 9 and 10 in the dis tcnded condition as shown in FIG. 2. In passageways 24 controlled by filter bags 11, 12 and 13 of FIG. 2 the gas flow would be maintained since the bags ll, 12 and 13 are shown in flaccid condition as will hereinafter be more fully explained.

Referring again to FIG. 2 it will be seen that the bags 8 through 13 are positioned centrally with respect to the open ends of the passageways 24 and that the end ones and the central one of the curtains 22 of the illus trated portion are longitudinally extended (upwardly in FIG. 2) as at 22, beside bags 18 and 13 and between bags 10 and I I to provide more complete sectionalization of the precipitator portion represented in FIG. 2 than would be possible if all of the curtains terminated at the same plane.

In FIGS. 3 and 4 bag valves 1 through 7 are shown as being supported centrally at the ends of the curtains 22 so that with bags 1, 2, 3 and 4 inflated as shown in FIG. 3 passageways 24 between curtains supporting the bags 1, 2, 3 and 4 will be closed off while those between 5, 6 and 7 are effectively completely open because of the deflated condition of the bags 5. 6 and 7. It is to be noted that with this arrangement there is no extension necessary on the curtains 22.

FIG. 4 shows the same precipitator portion as tha shown in FIG. 3 but this time the bags 1, 2 and 3 are in deflated condition while the bags 4 through 7 are inflated to cause sealing of the passageways 24 respective thereto. Thus, in FIG. 4 portion A of the precipitator is open and portion B of the precipitator is closed off for the cleaning interval of the cycle. This of course is all schematic representation in FIGS. 2, 3 and 4 of elongated, vertically extending cylindrical, flexible containers such as filter bags inflatable by means not shown in those figures and deflatable by similar means again not shown but in a well understood manner.

In FIGS. 1-4 and 10 each of the bags 1-13 is shown to be connected on its upstream side to a T-shaped stiffening element 27 extending longitudinally of the bag and fastened thereto to prevent downstream bowing of the bags when pressure differential is developed upon closure of the bag valves during a cleaning interval. FIG. 2 shows independent stiffeners 27 while FIGS. 3, 4 and 10 show such stiffeners fastened to the downstream edges of the respective electrode curtains 22 in which position the stiffeners 27 and connecting portions provide seal between the bags and the curtains 22 to prevent gas flow therebetween.

It is of course necessary that the bags be longitudinally tensioned as well as laterally stabilized to prevent abrasion of one bag by another when in contact with each other.

The representations of FIGS. 3 and 4 schematically illustrate the situation more practically illustrated in FIG. 1 wherein the bags in sections C and E to the left and right, respectively, as seen in FIG. 1 are illustrated as being in a flaccid condition and the arrows 26 in sections C and E indicate flow of gas between the deflated bag valves indicated at 16 in portion C and likewise in portion E. The bag valves of central section D indicated at 17 are shown as inflated and in contact with each other similar to the situation of bags 1, 2, 3 and 4 in FIG. 3 so that no air or gas is flowing through between the bags 17 of section D which is to be considered as being in the cleaning interval of the cycle with no air flow therethrough. The foregoing description of FIGS. 1 through 4 covers the basic idea of the principles of the instant invention while the remaining figures illustrate refinements of the basic idea.

FIGS. 5 and 6 illustrate one of the earliest pieces of information developed in working out the practical side of this invention wherein FIG. 5 shows the condition of a bag valve 28 when inflated so that it could be used in blocking a passageway. FIG. 6 shows the same valve as 28' when completely collapsed by evacuation of the air from within and it is to be seen that the blocking effect of the collapsed bag 28' of FIG. 6 will be almost the same as that of the extended bag 28 of FIG. 5 and this is to be noted as the action of the bags when the ends are maintained in a circular state by the prior art type of circular bag thimble.

FIG. 7 illustrates two non-circular mandrel shapes 29 and 30 which were successfully employed in controlling the shape of the bag valves as indicated by the shapes 29 and 30 of bags mounted on mandrel 29 and 30 respectively when such bags 29' and 30 were deflated. As can be observed either the eliptical shape 29 having length at least percent of its width (200 percent shown) or the elongated rectangle with rounded ends 30 provided acceptable operation of the bags when the longer dimension was parallel to the gas flow. It is to be noted that the circumference of the mandrel must be approximately that of the internal circumference of the bag when inflated. In this case the bags employed were of a nominal 11 /2 inches diameter and the mandrel of the shape shown as 30 which fitted the interior of such a has was approximately 4 inches wide and 16 inches long to fit the interior of a 11 /2 inch bag.

Referring now to FIG. 9, bags 32 fitted on mandrels 30 as seen in FIGS. 9 and 10 in the inflated state fit together nicely throughout their entire length except for the extreme top and bottom portions as at 33 where there was developed, due to the narrowness of the mandrel 30, an arrowhead shaped opening 34 between the bottom end portions of the bags 32 and also between the top end portions (not shown) of the bags 32. Although this was a relatively small percentage of the passageway area it was thought best to fill this opening as by an arrowhead shaped insert indicated at 35 of any gas impervious material such as fiber or plastic which would not injure the bags in case of contact therewith.

Another way of dealing with the openings 34 between end portions of the bags 32 is by a curtain 38 (FIGS. 9 and 10) of gas or particulate impervious material hung from a level above the openings 34 down to the floor of the precipitator on the upstream side of the bags 32 as best seen in FIG. 10 to prevent flow of gas or dust through the openings 34. Of course, in the case of the ceiling subjacent openings, if it is desired to close those also, the curtain 38 would be hung from the ceiling down in an obvious manner. The curtains 38 will be slit as at 39 to accommodate the stiffeners 27 or electrode curtains 22 as may be necessary.

FIGS. 11 and 12 illustrate another way of dealing with gas leakage between bag end portions by eliminating openings 34 through use of a mandrel 40 at each bag end which although eliptical in cross section would be as wide at its minor diameter as the passageway 24 so that a series of mandrels 40 with their respective bag valves 41 installed thereon would close the tops and bottoms of the passageways 24 with no space therebetween. In order to have a 11 /2 inch diameter bag fitted over a mandrel having a length of 17 inches and a width of approximately 9 inches the bottom end of the bag must be flared as at 42 to provide an internal circumference of approximately 41 inches. Many methods of providing such flared or bell bottom end portions are possible. For example. an axial split about 36 inches long on each of the opposite side of an end portion is shown in FIG. 12 to have a tapered gore 43, about 3 inches acrossat the wide end and about 36 inches long, set into the bag end portion on each side to provide the amount of circumference necessary to fit an 11 /2 inch diameter bag over a 9 by 17 inch eliptical mandrel such as 40. With such dimensions it is to be seen that the mandrel 40 each being equal to the width of a passageway 24 can be arranged either in the configuration of FIG. 2 or in that of FIG. 3 and still cover the totality of the passageways 24 which are each 9 inches wide.

As a mater of fact it has been found quite practical to slightly overlap mandrels 46 and 47 of two different heights as shown in FIG. 13 so that only a very tiny area from the floor up to the actual mandrel overlap as seen in FIG. 13 at 44 will remain and this small opening 44 can readily be completely closed by a plug element as shown at 45. Such a plug could be made of an inflexible material such as cast-in-place epoxy or silicone compounds or foams and caulking materials wedged into place or any other suitable material able to withstand the pressure differential and the other environmental conditions and formable into the shape 44 in a well known manner.

In FIGS. 11, 12 and 16 there is also shown development of the stiffening support illustrated in FIGS. 11 and 12 as an elongated flexible connecting element 56 of fiber glass cloth or the like fastened to the downstream edge of the curtain 22 as by rivets and eyelets 47 and to the upstream surface of the bag 41 as by cementing and/or sewing. Such a flexible connection will allow an increase in the upstream-downstream dimension of the bag when deflated and will maintain the vertical straightness of the bag when inflated and subject to pressure differential from interrupted gas flow. The element 56 will also seal the opening between the bag 41 and its respective curtain 22 when used in the FIG. 3 configuration.

FIG. 16 shows a different method of stiffening wherein fiberglass coth bands 60 or the like, encircling the bag 41 at axially spaced locations, and sewed thereto, are fastened by rivets and eyelets 61 to the downstream portion of the T-shaped stiffening element 27 or the edge an electrode curtain 22 (not shown) to prevent downstream bowing as above described most likely to be employed in the FIG. 2 configuration.

A still further development of the bell bottom idea resulted in a mandrel shape such as that shown at 46 in FIG. 14 which can be described as having an eliptical cross section with flattened portions giving the effect of a diamond cross section with rounded corners having a minor cross dimension or width equal to approximately the 9 inches of standard plate spacing with a length of approximately 19 inches in the major dimension to give the proper shape for complete flattening of the bag valves when deflated. Such action is seen in FIG. 13 where the mandrels 46 are indicated as overlapping and completely closing the gaps such as those shown at 34 in FIGS. 9 and and yet the bags when collapsed as shown at 50 (FIG. 13) will give excellent free space for gas flow therebetween and of course will close the gaps therebetween as shown in' FIG. 3 when inflated.

It is to be noted that the term inflation here means only a slightly greater pressure within the bags than that outside of the bags probably never exceeding a pressure differential of more than 1 inch of water gage pres sure and either clean or dirty gas can be used. Similarly deflation producing the flaccid condition is to be understood as including pressure differentials within the range from zero to one tenth inch water gage lower within the bags within the precipitator. Also, the material of the bags can be gas impervious or somewhat porous providing the inflation supply system has sufficient capacity to be capable of maintaining such a pressure differential at the prevailing leakage rate. If porous bags are used such bags may be rendered substantially gas tight by using dusty precipitator inlet gas for inflating such bags so that pores are plugged by precipitated dust. Obviously, any leakage gas from the bags will have been cleaned by passing through the bag fabric and such leakage will not degrade cleaner efficiency.

FIG. 15 shows a cross section of the mandrel 46 to illustrate the formed horizontally outwardly extending ridge 48 which extends all the way around the mandrel 46 near its upper extremity as seen in FIG. 15 to provide for anchoring the bags 50 in a well known manner.

It is further to be noted that the treatment shown for bottom bag end portions is equally applicable to top bag end portions and is so applied whether straight with arrow shaped inserts 35 as in FIGS. 9 and 10 or the curtains 38 of the same figures or flared ends 42 on eliptical mandrels 41 as in FIGS. 11 and 12 or on diamond shaped mandrels 46 and 47 as in FIGS. 13-15. It is further contemplated that straight sided bags of large enough diameter to accommodate the mandrels 41 or 46 and 47 could be used without flared ends to apply the principles of this invention.

It is, of course, necessary that provision be made for longitudinally tensioning the bags to prevent flapping and possible inter bag abrasion. but, since such tensioning is well known, it is not herein shown or described.

The operation of the precipitator 20 constructed according to the principles of this invention is entirely similar to that of the prior art precipitators except for the cleaning cycle which will be hereinafter described. Of course during normal operation the electrodes 23 will be charged to a high potential difference perhaps as much as 35,000 volts with respect to the normally grounded collecting electrode curtains 22. Suitable inlet ducting (not shown) will provide connection to a source of dusty gas such as a smoke flue or other source of particulate products which dusty gas will be cleansed as it passes through the passageways 24 in a well known manner.

After a suitable period of operation when dust has collected on the curtains 22 the bags 16 associated with sections C and E of FIG. 1 will be kept deflated while the bags 17 of section D will be inflated to shut off the passageways 24 between the bags 17 as shown so that gas flow therethrough is stopped. While the gas flow is stopped it is desirable that the electrodes 23 in that section of the precipitator be disconnected from the source of potential difference and allowed to become neutral. As soon as this has happened the curtains 22 of that particular section D will be vibrated, as by rapping, and the dust having been shaken loose from the curtain 22 will fall to the bottom of the hopper to be taken away in a well known manner. As soon as the dust shaken off the curtains 22 has settled to the bottom of the section D the respective electrodes will be reenergized, the bags 17 will be deflated and become flattened as shown at 50 in FIG. 13 so that the air will pass therethrough again. In a similar manner gas flow through section C and section E will be shut off, the sections rapped and reopened to provide the necessary cleaning of the respective curtains 22.

As can well be seen the rapping and cleaning of the curtains 22 of the above outlined method will be accomplished with no puffing and with superior cleaning of the curtains due to the removal of charges from the plates before the rapping begins.

It is to be noted that in FIG. 1 there is shown a pair of gas conducting conduits 52 and 54 extending horizontally across the precipitator under the bottom mandrel ends of the bags 16 and 17 in gaseous communication therewith. Conduit 52 is connected to a source providing low pressure therewithin, in the range from equal typically to about .04 inch water gage below the pressure within the precipitator. Conduit 54 is connected to a source of pressurized gas typically in the pressure range of 0.3 to 1 inch water gage above the pressure within the precipitator. By suitable valving, subdivision and manifolding (not shown) conduits 52 and 54 can be connected to and disconnected from the bags 16 and bags 17 (alternately) in proper sequence to, at one time, furnish pressurized air from conduit 54 to the interior of the bags 16 or bags 17 and at another time in the cycle to connect the bags 16 or bags 17 to the conduit 52 for removing air from the inside of the bags 16 or bags 17 to cause the collapse of those bags at the proper time.

It is, of course, possible that certain conditions of construction might make it desirable to place either or both of the conduits 52 and 54 above the bags 16 and 17 and have them communicate with the bags from above.

For example conduit 52 can be connected to bags 16 by manifolding, while conduit 53 is similarly connected to bags 17. Each conduit will then be connectable to a source of gas at positive pressure and alternatively connectable to a source of negative pressure as desired.

Although the foregoing description has been limited to application of the present invention to an electrostatic precipitator it is to be realized that such description is exemplary and not limitative and that the bag valve system of this invention is applicable for controlling gas flow through passageways of varied shapes and for various purposes by partial or complete valving of such passageways. v

Preferred embodiments of the expanding bag valves of this invention having hereinabove been described and illustrated it is to be realized that variations in the application of these principles are expected and envisioned and all of such variations are to be considered applications of the principles of this invention. It is respectfully requested that this invention be interpreted as broadly as possible limited only by the scope of the claims appended hereto.

What is claimed is:

1. A flow control system for an electrostatic precipitator having an assembly of parallel vertically extending laterally spaced collecting curtains carried within a housing comprising; a plurality of elongated flexible substantially cylindrical vertically extending inflatable containers secured within said housing in juxtaposition with each other and respective ones of said curtains to shut off gas flow between certain of said curtains when the ones of said containers respective to said certain curtains are inflated and to allow substantially free gas flow between said curtains when said containers are deflated, means for alternatively inflating certain of said containers and means for simultaneously deflating other of said containers, and said containers extending between and being connected to top and bottom mandrel elements, at least a portion of each of said mandrel elements adjacent the connection between a respective mandrel element and container being of non-circular cross section, said portion having a maximum trans verse length at least one and three quarters as great as the maximum transverse width thereof.

2. A flow control system as specified in claim 1 wherein said containers are fabric bags.

3. A flow control system as specified in claim 2 wherein a plurality of said bags and said curtains forms one valved section of such an apparatus and a second such plurality forms a second of such valved sections and means is provided for inflating and deflating said first plurality of bags and said second plurality of bags independently of each other.

4. A flow control system as specified in claim 2 wherein said mandrel portions are generally elliptical in cross section and are elongated in the direction of flow through said precipitator.

5. A flow control system as specified in claim 2 wherein each of said bags is fastened to a downstream end of one of said curtains and is at least vertically coextensive therewith.

6. A flow control system as specified in claim 5 wherein said maximum width of said non-circular shape is less than the spacing between said curtains and spaces between end portions of said bags are filled with dust stopping material.

7. A flow control system for a gas handling apparatus having at least one gas conducting passageway therein comprising: at least one elongated flexible substantially cylindrical inflatable container located at adjacent one end portion of said passageway, means for inflating said container to stop gas flow through said passageway, means for deflating said container to allow substantially free flow throughsaid passageway, said container extending between and connected to top and bottom mandrel elements, at least a portion of each of said mandrel elements adjacent the connection between a respective mandrel element and container being of non-circular cross section withsaid portion having a transverse length at least as great as the width thereof.

8. A flow control system as specified in claim 7 wherein said at least one passageway is a plurality of passageways and said at least one container is a plurality of fabric bags respectively associated with said passageways.

9. A flow control system as specified in claim 7 wherein said mandrel portions are generally elliptical in cross section and are elongated in the direction of flow through said gas handling apparatus.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3 3 900 299 DATED August 19 1975 mvgmoms) Charles W. Spehrley, Jr.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 4, line 18, change "bas" to bag Col. 5, line 22, change "47" to 57 Col. 5 line 37, after "described" insert a comma Claim 1, line 13, delete "means for simultaneously".

Claim 3, line 2 before "plurality" insert first Claim 7, line 4 delete "at".

Signed and Scaled this twenty-fifth Day of November 1975 [SEAL] A ttest:

RUTH C. A SON C. MARSHALL DANN Atrestrng Ojjrcer Commissioner nj'Patents a m1 Trademarks 

1. A FLOW CONTROL SYSTEM FOR AN ELECTROSTATIC PRECIPITATOR HAVING AN ESSEMBLY OF PARALLEL VERTICALLY EXTENDING LATERALLY SPACED COLLECTING CURTAINS CARRIED WITHIN A HOUSING COMPRISING: A PLURALITY OF ELONGATED FLEXIBLE SUBSTANTIALLY CYLINDRICAL VERTICALLY EXTENDING INFLATABLE CONTAINERS SECURED WITHIN SAID HOUSING IN JUXTAPOSITION WITH EACH OTHER AND RESPECTIVE ONES OF SAID CURTAINS TO SHUT OFF GAS FLOW BETWEEN CERTAIN OF SAID CURTAINS WHEN THE ONES OF SAID CONTAINERS RESPECTIVE TO SAID CERTAIN CURTAINS ARE INFLATED AND TO ALLOW SUBSTANTIALLY FREE GAS FLOW BETWEEN SAID CURTAINS WHEN SAID CONTAINERS ARE DEFLATED, MEANS FOR ALTERNATIVELY INFLATING CERTAIN OF SAID CONTAINERS AND MEANS FOR SIMULATANEOUSLY DEFLATING OTHER OF SAID CONTAINERS, AND SAID CONTAINERS EXTENDING BETWEEN AND BEING CONNECTED TO TOP AND BOTTOM MANDREL ELEMENTS, AT LEAST A PORTION OF EACH OF SAID MANDREL ELEMENTS ADJACENT THE CONNECTION BETWEEN A RESPECTIVE MANDREL ELEMENT AND CONTAINER BEING OF NON-CIRCULAR CROSS SECTION, SAID PROTION HAVING A MAXIMUM TRANSVERSE LENGTH AT LEAST ONE AND THREE QUARTERS AS GREAT AS THE MAXIMUM TRANSVERSE WIDTH THEREOF.
 2. A flow control system as sepcified in claim 1 wherein said containers are fabric bags.
 3. A flow control system as specified in claim 2 wherein a plurality of said bags and said curtains forms one valved section of such an apparatus and a second such plurality forms a second of such valved sections and means is provided for inflating and deflating said first plurality of bags and said second plurality of bags independently of each other.
 4. A flow control system as specified in claim 2 wherein said mandrel portions are generally elliptical in cross section and are elongated in the direction of flow through said precipitator.
 5. A flow control system as specified in claim 2 wherein each of said bags is fastened to a downstream end of one of said curtains and is at least vertically coextensive therewith.
 6. A flow control system as specified in claim 5 wherein said maximum width of said non-circular shape is less than the spacing between said curtains and spaces between end portions of said bags are filled with dust stopping material.
 7. A FLOW CONTROL SYSTEM FOR A GAS HANDLING APPARATUS HAVING AT LEAST ONE GAS CONDUCTING PASSAGEWAY THEREIN COMPRISING: AT LEAST ONE ELONGATED FLEXIBLE SUBSTANTIALLY CYLINDRICAL INFLATABLE CONTAINER LOCATED AT ADJACENT ONE END PORTION OF SAID PASSAGEWAY, MEANS FOR INFLATING SAID CONTAINER TO STOP GAS FLOW THROUGH SAID PASSAGEWAY, MEANS FOR DEFLATING SAID CONTAINER TO ALLOW SUBSTANTIALLY FREE FLOW THROUGH SAID PASSAGEWAY, SAID CONTAINER EXTENDING BETWEEN AND CONNECTED TO TOP AND BOTTOM MANDREL ELEMENTS, AT LEAST A PROTION OF EACH OF SAID MANDREL ELEMENTS ADJACENT THE CONNECTION BETWEEN A RESPECTIVE MANDREL ELEMENT AND CONTAINER BEING OF NON-CIRCULAR CROSS SECTION WITH SAID PORTION HAVING TRANSVERSE LENGTH AT LEAST 175% AS GREAT AS THE WIDTH THEREOF.
 8. A flow control system as specified in claim 7 wherein said at least one passageway is a plurality of passageways and said at least one container is a plurality of fabric bags respectively associated with said passageways.
 9. A flow control system as specified in claim 7 wherein said mandrel portions are generally elliptical in cross section and are elongated in the direcTion of flow through said gas handling apparatus. 